Abstract:

Because of the upper soil mass relative moving to the lower soil mass beside the ground fissure, there is the complicated action mechanism between lining structure and wall rock of soil with fissures. For investigating the engineering behaviors of Xi’an metro tunnel crossing ground fissures widely distributing the Xi’an zone, the physical model experiment with geometric proportion of 50:1 is carried out by reasonably simulating the wall rock stratum with a oblique ground fissure, lining structure, stress conditions and dislocation displacement of ground fissures. In the physical model experiment, the angle between axial of tunnel and direction of fissure equals to 450, the additional vertical stress of wall rock soil equals to 50 kPa, 100 kPa and 150 kPa respectively; and the tunnel is simulated with the similar material. The pressure of wall rock, settlement and internal stress of lining structure are measured by the new earth pressure sensor, displacement transducer and strain sensor in the processor of movement of ground fissure, so that the mechanical characteristics of wall rock and lining structure are analyzed well and truly. Test results show that the oblique ground fissure gets a larger sphere of influence on metro tunnel; and the settlement of deformation joints is developing significantly. In addition, the lining obliquely crossing ground fissures is in a force state similar to "beam", which will produce a rotating shift with the uniform settlement of tunnel lining. As to the development of ground fissures’ dislocation displacement, internal forces of lining are changed significantly with the changing of wall rock pressure; and both of the wall rock pressure in the foot wall and the wall rock pressure at the top of lining in the hanging wall increase, while the wall rock pressure at the bottom of lining in the hanging wall decrease. Comparing with the situation of the tunnel orthogonally cross ground fissures, the wall rock pressure and the internal force of lining structure changed larger when the tunnel obliquely crossing the movement ground fissure; and the lining structure is more prone to tensile failure.

Key words: ground fissure, metro tunnel, lining structure, physical model experiment